Two seat helicopter build.

I did indeed have the Pro Drive cog belt system, but in all fairness the factory stock chain drive had secondary shaft failures as well. I witnessed one of these failures when I was at the factory for flight training. And the chain drive imparted much less bending moment on the shaft than the cog belt did/does.

Running a cog belt loose is the not the answer either. I used this logic early in my flying career, and my shaft still failed. If it is too loose, the teeth of the belt can ride up on the teeth of the sprocket imparting instantaneous catastrophic tension/stresses. Finding the "happy spot" that keeps the cog belt from tightening too much due to sprocket expansion, and running it too loose is very elusive.

You should check out the EPI engineering web site. I persuaded Jack Kane to look into this issue after my secondary shaft failure. He did exhaustive finite element and stress analysis of this issue and other issues on this helicopter. He is active in the Reno Air Race community, and designs power plants and PSRU's (propeller Speed Reduction units). Link below:

http://www.epi-eng.com/

Many builders have been putting Solar T62 turbine engines in Rotorway helicopters for years, and I think that's the stock engine they use in the Helicycle. Do a Google search on Jet Exec and Helicycle.

Be advised, BJ schramm the developer of the Rotorway helicopter and more recently the Helicycle spent his lifetime designing and building helicopters. He ultimately died in one of them. If you're objective is to design and build that is one thing, but if you're doing this as an inexpensive way to get into flying helicopters, you're better off just buying one.
 
jmarkwolf said:
I did indeed have the Pro Drive cog belt system, but in all fairness the factory stock chain drive had secondary shaft failures as well. I witnessed one of these failures when I was at the factory for flight training. And the chain drive imparted much less bending moment on the shaft than the cog belt did/does.

Running a cog belt loose is the not the answer either. I used this logic early in my flying career, and my shaft still failed. If it is too loose, the teeth of the belt can ride up on the teeth of the sprocket imparting instantaneous catastrophic tension/stresses. Finding the "happy spot" that keeps the cog belt from tightening too much due to sprocket expansion, and running it too loose is very elusive.

You should check out the EPI engineering web site. I persuaded Jack Kane to look into this issue after my secondary shaft failure. He did exhaustive finite element and stress analysis of this issue and other issues on this helicopter. He is active in the Reno Air Race community, and designs power plants and PSRU's (propeller Speed Reduction units). Link below:

http://www.epi-eng.com/

Many builders have been putting Solar T62 turbine engines in Rotorway helicopters for years, and I think that's the stock engine they use in the Helicycle. Do a Google search on Jet Exec and Helicycle.

Be advised, BJ schramm the developer of the Rotorway helicopter and more recently the Helicycle spent his lifetime designing and building helicopters. He ultimately died in one of them. If you're objective is to design and build that is one thing, but if you're doing this as an inexpensive way to get into flying helicopters, you're better off just buying one.
Click to expand...

I have looked at EPI several times over the past couple of years when I was researching auto conversions for aviation use by means of redrive. Looks like they like Aero Commanders. I like them too. They are fine airplanes.

This project being built from the ground up will always pose it's challenges. This game we play where we get a set of limited options to work with is where imagination and problem solving have to step up to the plate and find solutions.

As far as the breaking of shafts goes, there should have been an upper bearing to help remove moment stress off of it. That would have fixed it, at the cost of some extra weight. Personally, if it was my ship, I would have done that and been fine with performing that mod.

I read the NTSB for Mr. Schramm's crash. The investigation was more or les inconclusive and mechanical / engineering failure were not found to be the culprit. Quoted from the Probable Cause and Findings section of the report: "The National Transportation Safety Board determines the probable cause(s) of this accident to be: In flight collision with terrain for undetermined reasons.'

This is a good reminder that even though all seems to be in order, accidents can still happen. Helicopters have an elevated level of possible problems because they are dependent on so many moving parts performing correctly. I understand this and I am totally ok with that reality. If I was not, I would not have pursued a license for flying them :).

One of the features that I want for this helicopter is a long flight response. two twenty gallon tanks that can give me three hours flight time with a 20 minute reserve. Installing a low compression ratio centrifugal flow engine with only one compressor stage will not provide that for me. It will be blowing my economy out of its tail pipe. The T62T series of engines would be the only option to work with in that family. The obvious advantage would be the power to weight ratio and reliability. The downside is the loss of economy and I do not want to sacrifice X-country capability. This is why I opted for a piston engine.
 
Last edited:
I am no helicopter expert but I know something about prototypes. I would be concerned about the weird mechanical and/or fatigue failures that you could have with an unproven design. As you know, the interaction of parts and designs in such a complex machine can lead to failures that could only be predicted experimentally (Robinson main rotor blades.) Seemingly minor changes can become catastrophic due to unexpected interactions. Even if the machine initially flew perfectly, I would always be wondering when I might find a problem in flight. That would take the fun out of flying for me.

Please don't get me wrong. This is an awesome project! I am watching with great interest and I hope to see you succeed wildly!
Regards
Robert
 
Last edited:
rwm said:
I am no helicopter expert but I know something about prototypes. I would be concerned about the weird mechanical and/or fatigue failures that you could have with an unproven design. As you know, the interaction of parts and designs in such a complex machine can lead to failures that could only be predicted experimentally (Robinson main rotor.) Seemingly minor changes can become catastrophic due to unexpected interactions. Even if the machine initially flew perfectly, I would always be wondering when I might find a problem in flight. That would take the fun out of flying for me.

Please don't get me wrong. This is an awesome project! I am watching with great interest and I hope to see you succeed wildly!
Regards
Robert
Click to expand...

No, not at all. You bring up a very good point here. The simple answer is that I would have to ultimately be ok with the idea that this machine could destroy itself with me strapped to it. That is the nature of it and I am ok with that. Well, ok as in ok with doing everything in my power to prove my components air worthy through empirical testing. Math formulas are very static and the truth is that they can only be statistically accurate because between the pencil pushing and the flying machine are materials and processes that can alter the data and accounting for all that is a hard thing to do indeed.
 
7milesup said:
Have you looked into the Solar T62 or similar? Once you operate a turbine, you will never go back to piston.
Click to expand...

There are some 'kits' around that turbine...
This one comes to mind:

http://www.helicycle.com/

Know a guy that built one... nice machine!

The turbine was seriously de-rated (lowered output) for this application.
 
Too bad the helicycle is one person bird. My thought on the turbine is if I was building a helicopter, I would try my best to find a way to use a turbine. The MTBF on a turbine is quite high vs piston, along with complete lack of vibration. But, I only gave building a heli a cursory glance because I figured it was out of my budget, along with the fact that I lost my medical certificate. Not sure if I can fly under the new med rules or not.

The aircraft in my avatar is what I flew for 15 years. We used to joke that it had 3 APU's because the two main engines (Garrett TFE-731's) were used as APU's on the DC-10 along with our APU which was a Garrett GTCP 36-150. The Solar T62T-40 was installed on some earlier Hawkers but my understanding is that the Solar did not provide quite the performance as the Garrett. *I wonder how much a Garrett GTCP would be?* ;)
 
I am waiting for the weather to warm up a little bit more before I start doing some more work on the airframe. It has been almost ridiculous in Ohio in terms of the weather. Looks like in a few days it should start to average in the 40's instead of the 20's. I'll break out and make my move then.
 
7milesup said:
The aircraft in my avatar is what I flew for 15 years. We used to joke that it had 3 APU's because the two main engines (Garrett TFE-731's) were used as APU's on the DC-10 along with our APU which was a Garrett GTCP 36-150. The Solar T62T-40 was installed on some earlier Hawkers but my understanding is that the Solar did not provide quite the performance as the Garrett. *I wonder how much a Garrett GTCP would be?* ;)
Click to expand...

My AP school has one of those Hawkers with two TFE's on it. The one on your avatar looks way better as ours looks really sad.
 
petertha said:
Can you elaborate on this? I don't have a TIG yet but many late nights of YouTube lurking, seems like TIG is the 'metal glue' of choice for all sorts of vehicles in tough or similar vibration environments - carts, race car chassis, motorcycles... Aside from some aluminum alloy bikes I don't see much mention of post heating unless related to alignment tweaking. But I am a complete newb. Is it because of thinner wall thickness 4130 tube more prevalent in aviation or..?
Click to expand...
i know ziltz about aviation but i do know that back in the day-preww2, ww2 and up until the 90's almost all aircraft was welded with o/a
 
You must log in or register to reply here.
Back
Top